Crossing the line, a tradition that dates back to ancient times when ships first sailed the world. The "line" is the equator. And If you've crossed it, and gone through the initiation, then you are a Trusty Shellback. If you haven't, then you are a lowly, slimy pollywog.
Exactly how a pollywog becomes a Shellback differs from ship to ship. It really is at the discretion of the Shellbacks as to what the pollywog must go through for most of the day. However, there are a few mandatory steps in the ceremony that are usually performed.

The day we crossed the equator aboard the Coral Sea it went something like this:

Report to duty station. Put clothes on inside out with skivvies on the outside. A big "P" gets painted on your back. You're led around to other compartments where Shellbacks are waiting to apply various fluids, grease, saw dust, dirt and whatever else they can find. They put it in your hair, on your face and all over. You have to roll in it, beg for more and like it. You are constantly asked questions and no matter the answer it is always wrong. This usually gets you swatted with a piece of wet fire hose or more substances are flung at you. After about an hour or two of this its time to move up to the flight deck. By this time you're completely covered in "goo" and sore from walking like a duck, crawling and getting swatted. But somehow your all still laughing your asses off at all of it, but not as much as the Shellback's are!
We're all paraded out onto the elevator and told to keep down and don't look up. As the elevator starts up fire hoses from the flight deck are trained on the latest pack of "wog's" to come topside. We're paraded off the elevator and put in a long four wide line waiting to go through the final hazing at the hands of the Shellback's. As we inch along we're pulled out of line every so often to do things like blow water out of a pad eye, lay on your stomach with your arms straight out till they burned and other such things. Finally your put in a stockade and the Shellback's start their interrogation to see if your worthy to go before the His Royal Majesty, King Neptune, you're not. Of course, there isn't a thing you can say that will prevent you from getting swatted over and over. Next you crawl over to King Neptune and his Royal Court. More "fun" is in store as you are once again interrogated and made to beg the King to become a Shellback. He finally agrees but not before you kiss the Royal Baby's belly, which is huge and covered in grease. It's not over yet. You must have your pitiful pollywog body cleansed of all its slime. This can only be accomplished by crawling and swimming in, of all things, slime. First you must crawl through a garbage chute that is knee deep in two-week-old garbage. For those of us that came along later in the day it had the additional ingredient of guys that got sick from the stench. If that didn't get you the last step was to jump into a makeshift tub that was filled with rotten bug juice, seawater and other god-awful liquids. You have to dunk your head under and crawl to the other end. If you try and get out too fast or come up too early or just for no reason you have to do it again. Finally, you emerge from the tank. There are some firehose's set up spraying straight down at full force. You strip just about everything off and throw it overboard. Take a shower, which does hardly anything, but your done.
Your sore from being swatted, crawling on the deck and walking like a duck. Your covered in absolutely the most disgusting "stuff" from head to toe. You've been humiliated from start to finish. But somehow you're all still laughing your asses off at all of it, but not as much as the Shellback's are! Hey wait a minute, you made it, you're a Shellback too!!!